1. Field of the Invention
The present invention relates to a transfer driver device for a pressing machine, and particularly to the transfer driver device which employs a plurality of precision positioning cylinder devices and a common minimum capacity hydraulic supplier means.
2. Description of the Related Art
Transfer pressing machines are provided with transfer driver devices, and transfer mold materials (semi-finished products) through multiple stages in a sequential and automated manner.
Included in these transfer pressing machines are two types: one is a two-dimensional type which allows feed bars to move in advance/return mode and clamp/unclamp mode and the other is a three-dimensional type which allows feed bars to move in above two modes plus lift/down mode. In both types, since the motion of the feed bar must be in cooperation with the up and down stroke of a slide, the feed bar is driven by a link mechanism, a rack and pinion mechanism, a planetary gear mechanism or the like through a crank mechanism and rotating cams which rotate in synchronism with a crank shaft.
Such mechanical transfer driver devices have been disclosed by Japanese Utility Model Laid Open No. 61-122028, Japanese Utility Model Application Publication No. 63-17540, Japanese Utility Model Application Publication No. 63-24776 and Japanese Utility Model Laid Open No. 2-93030.
A motor-driven transfer driver device, as opposed to the above mechanical transfer driver devices, is proposed, for example, in Japanese Patent Application Publication No. 63-22895. In such a motor-driven transfer driver device, a reversible variable-speed motor is used as a mover. To drive feed bars, the rotary motion of the motor is converted into linear motion by means of a rack and pinion mechanism, ball screw, splined shaft or the like.
The conventional mechanical transfer driver devices described above need a number of parts, and are bulky and complex in construction and thus costly to manufacture. Furthermore, switching of the feed stroke and the feed rate is normally difficult. In the conventional mechanical transfer driver devices, insufficient room is provided for achieving a compact and low cost design and adaptability to a diversity of applications.
In contrast, the motor-driven transfer driver devices are more flexibly adapted to compact and low cost design. From the viewpoint of cost, however, the motor-driven transfer driver devices do not necessarily satisfy low cost design requirements because the rack and pinion mechanism for converting the rotary motion into the linear motion remains costly. Furthermore, each of the feed, clamp and lift modes needs its own dedicated motor and associated driver control device, requiring a large scale power supply system. This leads to a poor operating efficiency, jeopardizing power saving efforts.
Proposed as another mover is a hydraulic generator device which uses cylinder mechanisms on each of which a plurality of cams is coaxially disposed. The rotation of the cams drives a corresponding cylinder mechanism. The use of such a device is not widespread, because the construction of the device, except the mover portion, needs a number of parts and thus the device itself becomes costly.